In a stunning slap at the Father of our Country, stone carvers got George Washington’s words wrong on the landmark Manhattan Supreme Courthouse, The Post has learned.

“The true administration of justice is the firmest pillar of good government,” reads the inscription chiseled in granite above the fluted columns at 60 Centre St.

But the nation’s first president actually penned the word “due” – not “true” – according to centuries-old documents on file at the Library of Congress and National Archives in Washington, DC.

The mangled motto adorns one of the world’s most recognizable halls of justice, whose imposing Roman facade appears in the movies “The Godfather,” “12 Angry Men” and “Miracle on 34th Street,” as well as countless episodes of the various “Law & Order” TV series.

City and court officials were unaware of the outrageous rewrite until contacted by The Post.

“It’s a shame,” said longtime New York County Clerk Norman Goodman, who has worked in the six-sided courthouse since 1969.

A spokesman for the Department of Citywide Administrative Services, which manages the Foley Square building, blamed Boston architect Guy Lowell, who won a 1913 design competition. He died in 1927, the same year the courthouse opened.

Washington, who took the presidential oath of office at nearby Federal Hall, coined the phrase in a Sept. 28, 1789, letter drafting fellow Virginian Edmund Randolph as the nation’s first attorney general.

Washington expert Philander Chase, who spent 35 years editing the Revolutionary War hero’s papers, said the engraved phrase doesn’t even sound like his style.

” ‘True administration’ is probably what we would say today, but ‘due administration’ is more what they would have said in the 18th century,” said the recently retired University of Virginia professor.

James Rees, executive director of Washington’s estate and gardens in Mount Vernon, Va., said the bumbled quotation joins a laundry list of slights against the American icon – most notably today’s “Presidents Day” holiday, created after Congress changed the observance of his actual Feb. 22 birthday in 1971.

Rees said the court error should be corrected.

“Washington was a real stickler for detail. He wasn’t one to let small things slide, so it would make a little bit of difference to him that they got this one right,” he said.

A fix would need approval from the city Landmarks Preservation Commission, which safeguarded the courthouse exterior from alteration in 1966.

County Clerk Goodman, whose office distributes brochures about the historic building, said he would immediately print new ones noting the mistake.